Composites and method for making

ABSTRACT

CARBON FIBER PREPREGS CONVERTIBLE TO CARBON FIBER-CARBON MATRIX COMPOSITES ARE POVIDED AND A METHOD FOR MAKING THEM. CARBON FIBER TOWS ARE TREATED WITH ACETYLENIC ORGANIC RESIN AND THEREAFTER CARBONIZED TO A HIGH STRENGTH COMPOSITES.

Patented May 7,, 1974 3,809,673: COMPOSITES AND METHOD FOR- Dwain M. White, Schenectady, Howard, J, K lopfer,

Elnora, and Joseph R. McLaughlin, Burnt assignors to General Electric Company j.. a 1 236,191 Int. Cl. C08 f 45/28 No Drawing. Filed Mar. 20, 1972, set. N

US. Cl. 26042.1 6

High strength composites.consisting-of anorganic ma- 15,5.-

trix and a reinforcing fiber, such as glass-fiber, boron' fiber, carbon fiber, etc., have been viewed'with considerable in terest by the aircraft .industryand other industries interested in the employment of materials convertibleto -lightstrength and elastic modulus' Various combinations of one or more of the aforementioned'fibers 'and' orga'mc resins, such as epoxy resins and 'polyimideshavebeen evaluated extensively because thesematerials have -pro+ because the organic'matrix will decomposeand result in premature composite breakdowm (a l It has now been discovered that :earbo'n fiber prepregs and laminates consisting vessentially: ofcarbon 'fibers,' c ar= bon fiber tows treated with certair'iprganiei resin'shaving 25 weight shaped structures'having an'iinusually' hi'gh tensile :LE; xi 'l l' dgf b 411m tie mga the mole percent-of a and (b) is 100,

and w;

(B)(c) to 5 P rcentby weight of diethynyl units of the formula,

bascdpn theweight of (a) and (b), where R is a phenylene radical having. the valence bond in the meta position, or theparasposition, where the para phenylene radicals can be present at, up, to mole percent, based on the total moles of, meta and para phenylene radicals in the mixture,

where ,the .rcf maining valences of the phenylene radicals acetylenic unsaturation, defined hereinafter, can be converted to high strength carborrfiber-carbon :matriXi'composites which can be employed-at..temperatures aswhigh as 1500 C. under substantially non oxidizingconditions for extended periods of timei'Eveniwhe'n, employed in an cantbe substituted with up to four monovalent radicals selected,from hydrogen, alkylradicalahaving from 1 to 8 carbon atoms, halogen radicals,-and mixtures thereof,

B is a;divalent. organo radical'selected from hydrocarbon radicals having from 2 to 40 carbon atoms,

Y is selectedfrom I v I V radicals, Q is selected from monovalent hydrocarbon radica'ls' and halogenated monovalent hydrocarbon radicals,

R3 ,is'a trivalentaryl radical, R is selected from hydrogen and; monovalent'hydrocarbon radicals, such as methyl or phenyl, ar 1d z,. has a value of 0 or 1.

l 1a d ical s included by R'of Formulas 1 and 2 are, for examplqerylene radicals, such 'as phenylene, xylylene, tolylene; halogenated derivatives of such arylene radicals, such; as chlorophenylene,- chlorotolylene, bromoxylylene, F.---R=. di s, nel dedtby-rk r r f e p e afore mentioned R radicals, alkylene radicals, such as hexameth? ylene, heptamethyleng; octarnethylene; 'nonamethylene,

and radicalssuchas,

oxidizing atmosphere, suclr'as :air, :--the subject carbon I a the range of o about 175F599 vh e t JQ m t phenyl-trans-butenyne j1,3 bisP e iYl itadiynyl)benzene;

sists essentially of'from, y (a) to mole percent of diethynyl arylene units of theformula, :1 r '1 the formula,

' (b) o to 20 niole percent bi diethynyl units of Sorn'of the"substantially?non volatilealiphatically unsaturated organic-compoiiiids whichf can be employed as organic 'plasticizer ;in'-' the practice of the invention are l,4-diphenylbutadiyne, l,4&diphenyl cis-butcnyne, 1,4-dietc." I v t (The polya'cetylenes which'can be employed'to make the acetylenic organic-resin thepracfti'ce" of the invention are any organic polymer having chemically combined Formula 3 radicals' and' can consist essentially-of chemically co'mbiried'-=carbon atoms and "hydrogen "atoms, or chemically 'c'ombined carbon atoms, hydrogen atoms, and oxy- "gen atoms-and in {particular instances, in addition to the aforementioned atoms, chemically combined sulfur atoms, nitrogen atoms, and mixtures thereof.

in the practice of the invention, are-polymers containingin addition to Formula 3 radicals, divalent radicals derived from diethynyl aromatic compounds, such as diethynyl benzene. Some of these polyaoetylenes are' shown by Hay Pat. 3,300,456, and include polymers having chemically combined Formula 1 radicals.

In addition to polyaoetylenes having chemically combined Formulas l and 2 radicals, are polyesters having acetyleneic bonds in the chain also can employed as shown by Sladkov et al., Academy of Science, U.S.S. R.; Bulletin Chemical Science, 1220-1222 (12613)". Sor'n'efbf these polyaoetylenes can be made by reacting" a acetylenic dicarboxylic. acid and a diol such as he'xanediolY- Amongthe preferred olyacetylenes are polyac'etylene terpolyme'rs which can be made by reacting ethynylarylene compounds to provide units of Formula 1 such as meta-diethynylbenzene or mixtures of meta-di ethyn'yl benzene with para-diethynylbenzene in combination with compounds which can provide units of Fbr'r'nulaZ, such as dipropargyl ethers, diethynyl alkylenes, and optionally with acetylene to provide units of Formula 3, employing the oxidative coupling reaction disclosed in Hay Pat.

benzophenone,

3,300,456, "assigned to the same assignee as the present invention. There is employed in the oxidative coupling reaction, which will be shown more specifically in the examples set forth later, a basic cupric amine complex, and oxygen. A mixture for example, .of a dipropargyl ether of a dihydric phenol can be employed with a diethynyl aryl c ene mixture consisting for example, of meta-.diethynyl benzene and para-diethynylbenzene and employed in an oxygenated solution with an oxidative coupling catalyst such as cuprous chloride, N,N,N',N'-tetramethylethylenediamine with an appropriate organic solvent such as diventionalmeans with a solvent such as methanol and thereafter dried. When employing dipropargyl ether units in the reaction mixture, there is produced ether tel-poly mers while alkylene terpolymers-can be made by' using diethynyl alkylene compounds suchas 1',6'-diethynyl= hexane.

Among the ethynyla'rylene com'p"ounds' which; can? be employed to introduce units of Formula 1* "intothe tar: polymer, there can be utilized diacetylene monomers of the arylene and haloarylene series, which canbederived sponding divinyl aryleneslrsuch as 'div-inyl benzene, divinyl toluene, divinyl naphthalene, etc., and the'diethylarylenes such as diethylbenzene, diethylnaphthalene, etc.

Included by the dipropargyl ethers which can be employed to introduce units of Formula'2 into the terpolymer are reaction of products of a propargyl halide, "such as propargyl bromide, and-"dihydric phenols of the benzene, naphthalene, anthracene, etc." series, for example, hydroquinone, resorcinol, catechol, the isomeric dihyenes such droxynaphthalenes; the isomeric dihydroxyanthracenes,

etc., or they can be dihydroxy' substituted biphenyls or diphenyl ethers, e.g., for example, the various isomeric bisphenols, for example, 2,2',-biphenol,"2,3-biphenol, 2,4-

biphenol, 3,3'-biphenol, 3, 4 -biphenol, 4,4',- biphenol, the v isomeric ,bis(hydroxyphenyl) lethers, for example, -bis(2- hydroxy'phenyl) ether, bis(3-hydroxyphenyl) ether, his (4-hy droxyphenyl) ether, 2-(3-hydroxyphenoxy) phenol, l-( -hyd yph n y) phe l. v3-. y c'phm e!) phenol, '3-(4-hydroxyphenoxy) phenol, etc.,-

. These dihydric phenols canalso-be the isomeric (hydroxyphenyl), sulfones, or thevarious isomeric di hyd phe w as alkyleneor alkylidienediphenols for example, 4,4'-isopropylidenediphenol, 2,2 isopropyl ide'nephenol, ,2,4'-isopropylidenediphenol, methylenedihenol, ethylenediph'enol, ethylidenediphenol, p'ylethylene) diphenol, etc. p p

Any of the above dihydric phenols can be substituted byhalogen or a lower alkyl group.- i.e., to 1 to 8 carbon atoms, typical examples which are chlorohydroquinone, bromohydroquinone, tetrachlorhydroquinone, methylhydroquinone, ethylhydroquinone, isopropylhydroquinone, butylhydroquinone, pentylhydroquinone, hexylhydroqui none, includingcyclohexylhydroquinone, heptylhydroquinon'e, octylhydroquinone, etc., the corresponding halo and alkyl substituted catechols and resorcinols, etc., the halogen .andlower ,alltyl "substituted biphenols, the halogen and lower 'alkyl substitutedfbis-(hydroxyphenyl) ethers, thehalogen and lower alkyl substituted bis(hy droxyphenyl) sulfones, the halogen and lower alkyl substituted alkylene and alkylidene biphenols,etc.

In addition to the above dihydric phenols there also can be employed dihydric compounds containing a ketone'group such-as dihydroxybenzophenones, examples of which are, J2,2-dihydroxybenzophenone, 2,3'-dihydroxy- 2,3-dihydroxybenzophenone,v 2,4'-dihydroxybenzophenone, 3,3'-dihydroxybenzophenone, 3,4- dihydroxybenzophenone, 1 4,4'-dihydroxybenzophenone, 2,3'qdihydroxybenzophenone,. 2,4'-dihydroxybenzophenone, 2,4-dihydroxybenzophenone, 3,4'-dihydroxybenzo.- phenone, the dihydroxybenzils, the dihydroxyphenylnaphe thyl ketones the; phenyl .dihydroxynaphthyl 'ketones, the hydroxyphenyl hydroxynaphthyl ketones, etc., are those same, aryl ketones containing 1 or more halogens or lower alkyl substituents on thearyl group, examples of which are given above. g

, Likewise these acetylenic polymers can be dipropargyl 'ethers of ,alkylcarbonyl substitutedv dihydric phenols. The alkylcarbonyl substituteddihydric phenols can be any dihydric. phenol, numerous examples of which are given above, which also, contains one or more alkylcarbonyl (acyl) substituents. For example, 2,4-dihydroxyacetophenone, 2,3-dihydroxyacetophenone, 2,5-dihydroxyacetophenone, 2,4dihydroxypropiophenone, acetylbiphenols, diacetylbiphenols, etc.-

' Units of Formula. 2 in the form of diethylalkylene units cant,be;-introduced into the terpolymerto produce the alkylene terpolymer by the aforementioned oxidative coupling procedure of Hay, utilizing diethynyl arylenes as previously defined, in combination with diethynyl alklyas'1,5-hexadiyn'e,' 1,6-heptadiyne; 1,7-octadiyne, etc: Carbon-fiber which can be employed-in the practice of theinventionincludes fiber, derived from carbonized I v polyacrylonitrile, celluloseacetate, cellulose nitrate, etc. by halogenation then dehydrohalogenation of the corresuch. as-Morganite, Type I and II, Thornel 25, 40, 50 etc.,. fiberfimade: romamolten' polyvinyl chloride pitch, etc.i..

Further examples-of carbon fiber are shown in Johnson et al..Pat.3,41-2,062',.:iand polyacetylene fiber of Sliva et al.,-Ser.- No;v 86,295, filed Nov. 2, 1970, and assigned to the sameyassigneeasthe present invention. Polyacetylenes useful for making such carbon fiber are further shown by ,Hay Pats. 3;3.00,4;56; 3,332,916 and 3,519,611 assigned to the same assignee as the present invention, and French Pat. 1,557,383.';'lhesepolyaoetylenes are extruded in the form,o. a blend,-jand thereafter heated to a temperature up to-about-ZOOOfi C. to. produce 'a fiber having an elastic modulus ofi -up-to'about 15X16 p.s.i. The fiber then can be heated to-a temperature of up to about 3,30(l C., while'undena tensionv of up to about 1 1O p.s.i. to produce a h igh strength, high modulus fiber useful in making prepregs and composites in accordance with the present invention. I

In accordance with the practice of the invention, the

" carbon fiber is preferably treated with the acetylenic or vent, such asjchlor'obenzene and then heated in'a forced air furnace under" conditions to'feffect' the evaporatib'n of the organic solvent. Another technique which has been found to be effective is passing the carbon. fiber into a melt of the acetylenic organic resin in the form "of a mixture consisting of about 80% to 95 by weightiof the non-volatile acetylenic unsaturated plasticizer and to 20% of the polyacetylene'Etfective results utilizing the melt procedure can be achieved at temperatures in the range of from 100 C. to 140 CL It has been found that carbon fiber treated in the above described manner retains a unif ormcoating of the ace! tylenic organic resin. The coated fibershave a dry smooth surface and can be stored for an indefinite period of time in the dark at 5 C. When they aretogbe fabricated, they can be cut to the desiredlength, placed on a mold and heated under pressure. Under" the conditions of heat and pressure, the acetylenic plasticizer facilitates the flow of the acetylenic organic resin and the meltflows to fill in void spaces. The prepreg cures to a crosslinked network which can be carbonized with a low weightless by heating to temperatures up-to about 800 C.

Experience has shown the prepreg-can consistof a proportion of from about to 60% by weight of the of carbon fiber. It has also been found that'improved modulus and tensile strengths can be obtained in the resulting carbon fiber-carbon matrix composites when the-previously defined or-ganicplasticizers ;are used in combination with maleimides, such as N-phenylmaleimide, N,N+bismaleimido-4,4 .'-diphenylmethane, etc. in proportions of up to about 10% by weight of the acetylenic organic-resin. Incorporation of the maleimide into the acetylenic resin can be achieved in various ways, including direct addition into fiber coating solutions, dipping acetylenic organic resin treated fiber into organic solvent solutions of maleimide, etc. Y 1 n i In addition optimum properties also are obtained when the carbon-fiber-is pretreated with nitric acid vapors, to produce improved interfacial adhesion between the carbon fiber and the carbon matrix. Fiber pretreatment can be achieved by hanging the fibers in the vapors of reacetylenic organic resin and from 40% to 85% by weight fiuxing 60% nitric acids for,5 to l0 hours for high strength Morganite (Type II). fibers, and 2 to 4 days for high modulus (Type I) fibers.

It also has been found that the acetylenic organic resin can be employed in the above described manner to treat various metalfilaments, such as-tungsten, steel, 1:

aluminum, etc., alumina fibers, boron fibers, and-.silica fibers to produce composites of such fibers in a carbon matrix. Laminated 'structures'utilizing mica also are included within the scope of the presentinvention, in addition, to the aforedescribed fibers, additional beneficial .1

results also could be achieved by the employment of fillers, "such as graphite," powdered Teflon, molybdenum disulfide, siliconcarbide, diamond and boronnitride as well as antimony-compounds to impart such properties as improved lubricity, abrasive properties and flame re- 1:

tardants. The above described method is also" applicable to a continuous process wherein the coating OFtreatment of the fibers can be incorporated as a final step. The

prepregs can be pressed directly into composites of any desired shape. The coated fibers also can be woven into a cloth, which can have a uniformly distributedmatrix EXAMPLE 1 A terpolymer was made by employing dipropargyl ether of 2,2-bis(4-hydroxyphenyl) propane, (Bisphenol- A), meta-diethynylbenzene and para-diethynylbenzene utilizing 'an .oxidative coupling catalyst produced with cuprous chloride, N,N,N',N'-tetramethylethylenediamine, and a solvent system of pyridine and dichlorobenzene.

There was added a solution in about 25 parts of dichlorobenzene of 0.5 part of the dipropargyl ether of Bisphenol-'A,f 4.l parts of meta-diethynylbenzene, and 0.4 part of para-diethynylbenzene to a mixture of 0.15 part of lcuprous chloride, about 0.18 part of N,N,N',N'-tetramethylethylenediamine dissolved in an oxygenated solution of about: 1.7 parts of pyridine and parts of orthodichlorobenzene at 60 C. The temperature of the mixture rose, to 88.5 C. while it was stirred after about 2 minutes. The'mixture also became too thick to stir. After 10 minutes the mixture was allowed to cool to room temperature, and added to excess methanol containing a trace of hydrochloric acid. There was obtained a quantitative yield of product having an intrinsic viscosity in orthodichlorobenzene at 120 C. of 0.77 dl./ g. I The aboveprocedure was repeated except in the mixture employed to make the terpolymer, there was utilized phenylacetylene chain stopper to reduce the molecular weight as follows:

1 A terpolymer was made by employing dipropargyl ether of 2,2 bis (4 hydroxyphenyl) propane, (bisphenol-A), meta-diethynylbenzene and para-diethynylbenzene with phenylacetylene to control the molecular weight utilizing an oxidative-coupling catalyst produced with cuprous chloride, N,N,N',N-tetramethylethylenediamine, and a ,solvent system of pyridine and dichlorobenzene.

There was added a solution in about 50- parts of orthodichlorobenzene of 2 parts of the dipropargyl ether of bisphenol-A, 16.4 parts of meta-diethynylbenzene, 1.6 parts of para-diethynylbenzene and 2.54 parts of phenylacetylene to a mixture of 0.55 part of cuprous chloride, about 0.7 part of N,N,N,N'-tetramethylethylenediamine dissolvedin an oxygenated solution of about 6.8 parts of pyridine andlSO parts of ortho-dichlorobenzene at 60 C. The temperature of the mixture rose to 75 C. while it was stirred after about 8 minutes. After 10 minutes the mixture was allowed to cool to room temperature, and added .to excess methanol containing a trace of hydrochloric acid. There was obtained. a. quantitative yield of low molecular weight terpolymer having an intrinsic viscosity in orthodichlorobenzene at 120 C. of 0,l2 dl./g.

' Coating solutions were prepared from the above described polyacetylcne terpolymers with diphenyl butadiyne in chlorobenzene. The respective coating solutions 'consistedf'ofj"25%'by weight of's'olids. The'solids consisted.of 50% by-weight of the terpolymer and 50% by weight of thedimer. Bundles'of carbon fiber were passed throughtherespective coat-ingsolutions at C. which :was being agitated and while thefibers were-being flexed 'to. provide for' effe'ctive treatment of .the fiber surfaces with the coatingsolution. The wet fibers were then placed-immediately ina forced 'air oven at C. where they were hung to allow removal of solvent. The cooled fibers were found to have a smoothfglossy dry t qlvsi a u evapora ed-h... The coated fibers were: then placed in ,a rectangular mold with a piston having the dime'nsionsof by 2 /2". The fibers were thenmolded by placing the cold mold between preheated platens (300") in a press. When a temperature'of Cswas attained in the mold, pressure ofabout 2000 p.s.i. was applied and maintained for approximately" 10. minutesuntil ,the mold temperature reached 290 C. The molded bar was removed while the mold was hot.

Additional coating solutions were prepared where the dimer was varied over a proportion of from 50% to 80% by weight of the acetylenic organic resin. In addition varous carbon fibers were treated including Morganite I and Morganite II. The following shows the results obtained where the wt. percent terpolymer indicates the weight percent of either high or low molecular weight terpolymer utilized in the acetylenic organic resin emsurface after 7 ployed to treat the fibers, densityx (g./cm.), Flex (Flexural strength, p.s.i.) and Mod (Modulus x 10-) indicates properties of the composite.

iigher molecular weight terpolymer, intrinsic viscosity 0.77 was use 1 EXAMPLE 2 Coating solutions of the low molecular Weight terpo mer of Example 1, 1,4-diphenyl butadiene, and either N phenylmaleimide, or N,N'-'bismaleimido 4,4-diphenylmethane dichlorobenzene was prepared for dip coating various tows of Morganite I and II fibers. The coating solutions contained 25.5% of solids of 50% of terpolymer, 40% dimer and 10% of the N-phenymaleimide. The Morganite II fibers had been pretreated in the vapors of refluxing 60% nitric acid for 5 to hours and then washed with water and dried. The Morganite I fibers were treated similarly for 2 to 4 days. I i

The nitric acid treated fibers were then'treated with the above described coating solution by immersing the fibers in the dichlorobenzene coating solution with agitation. The treated fibers were then placed in an air circulating oven at 115 C. for minutes to effect the evaporation of the dichlorobenzene and allow excess resin solution to drip off. The dried tows were cut to 2 /2 lengths, placed lengthwise in a 2 /2" by 0.38" mold and pressed while the temperature was rapidly' raised from 125 C. to 290 C. over a period of about minutes.

The following table shows the results obtained with various types of carbon fibers utilizing coating mixtures containing various weight percents of either N-phenylmaleimide or bis-maleimde, where surface treatment show hours of nitric acid reflux, N-phenylmalmide wt. percent or bis-maleimide wt. percent shows these respective maleimide wt. percent in the acetylenic organic resin. In Table II, the weight percent of acetylenic organic resin in the various prepregs was essentially the same and approxi- B After nitric acid treatment the dried carbon fiber was dipped into a a Q .9. I 371':

1% solution of bis-maleimid LE A coating solution of the low molecular weight terpolymer of Example 1 (intrinsic viscosity, 0.l2dl./g.)' in molten diphenylbutadiyne'was prepared. The coatingsosile (p.s.i.) and modulus (p.s.i.). v s

. EXAMPLE 4 Molded bars of Example 2, containing 50 to a carbon fiber (from a nitrc acid treated Morganite I fiber ihdwith the N-phen'ylmaleimide additive) were heated 970 C. under nitrogen to carbonize the resin. The bars lo'st 3 to 6% of their total weight during the carbonization which corresponded to about a 12% weight loss for the resin portion. The flexural strength and modulns was 48x10 'and 19x10 p.s.i. respectively for a bar with 53% carbon fiber. Although "the above examples are limited to only a few of thejvery many curable compositions which can be made by the method of the present invention, it should be understoodthat the present invention is directed to a much broader class of acetylenic organic resin coniprisin'gpolyacetylene having chemically combined units of Formulas 1 -3 in combination with various acetylenically unsaturated organic plasticizers as previously defined.

What we claim and desire to secure by Letters Patent 'ofthe United States is: 1.- Curablecompositionscomprising carbon fibers oriented in a predetermined manner, which have been treated with acetylenic organic resin comprising:

\ (A) from 10% to 75% by weight of a polyacetylene terpolymer consisting essentially of chemically combined metadiethynlylbe'nzene, units, paradiethynylbenzene units, and Bisphenol-A dipropargyl ether units 1 -(B) "from 25% to by weight of 1,4-diphenyl butadiyne. I

'2. A curable composition in; accordance with claim 1 containing a maleimide selected from the class consisting 'of N-phenylmaleimide, N,N'-bismaleimido-4,4- bismaleimido-4,4'-diphenylmethane and mixtures thereof. 3. A curable composition in accordance with claim '1, Where (A) is-aterpolymer consisting essentially of 12 mole percent of chemically combined diethynyl butane units, 6 mole percent of chemically combined para-diethynyl-benzene'units, and 82'mole percent of chemically combined meta-diethynylbenzene units.

4. A curable composition in accordance with claim 1,=where the carbon fiber has been pretreated with nitric acid vapors.

. e ,References Cited UNITED" STATES PATENTS -"3,102,047'118/1963 Rivington 117 '46'cc 3,639,197 '2/1972 s am s 161-35 I 3, 8 2,595 .s/1972 Okuda 117-46 CC 3,799,863 1/1973 White mo -32.4

LIEBMAN, Primary Examiner P R. R-. MICHL, Assistant Examiner v T UsJCil m.

117"46CC, Dig. 11; 260-3316 UA, 42.17; 264 -29; 423-447 I, I 1 

